Download A force is a push or a pull on an object in a direction. In mechanical

A force is a push or a pull on an object in a direction. In mechanical
systems, forces can cause objects to move or change their motion. If a force
is exerted on an object at a distance from its axis of rotation, it creates a
torque. Torques can cause objects to rotate or change their rotational motion.
In fluids, we think of forces being distributed over areas. Pressure is the
force per unit area. Pressure differences in a fluid explain the buoyant force
an object feels when it is immersed in the fluid. In fluid systems, a pressure
difference can cause fluid to move or change its motion.
When electric charges are separated, each charge feels a force of attraction
or repulsion because of the presence of the other charges. The space
surrounding the electric charges can be thought of as an electric field. There
is a potential difference, or voltage, between two points in an electric field.
Voltage causes charge to move in electrical systems.
The temperature of a body is a measure of the average kinetic energy of the
random motion of the particles that make up the body. Thermal energy is the
total kinetic energy of all the particles. When two bodies with different
temperatures are brought together, thermal energy flows from the hotter
body to the colder body. The thermal energy transferred is called heat. In
thermal systems, a temperature difference causes heat to flow.
The table on the next page summarizes the four energy systems and the
prime movers—force, pressure, voltage, and temperature difference.
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C HAPTER 1
THE PRIME MOVERS
Energy System
Prime Mover
Mechanical
Translational Force
Units
SI
English
Quantity Moved
N
lb
Torque
N•m
lb • ft
Fluid
Pressure
N/m
lb/in2
Electrical
Potential
difference
V
V
Charge
Thermal
Temperature
difference
°C
°F
Heat
Rotational
Mass moved through a
distance
Mass rotated through an
angle
Fluid volume or mass
C HAPTER 1
SUMMARY
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